This invention relates to an outboard motor, and more particularly, to an improved outboard motor having a compact configuration and one in which the symmetry and balance of the motor is improved.
Conventional outboard motors generally are affixed so that they extend rearwardly of the transom of a watercraft and include a drive shaft housing in which a vertically positioned drive shaft is journaled for driving a propulsion unit in the lower unit to propel the watercraft. An internal combustion engine is normally mounted in a power head above the drive shaft housing and has its output shaft directly coupled to the drive shaft for driving the propulsion unit. Although this type of construction has advantages, it tends to move the center of gravity of the outboard motor to a relatively high location and provides a substantial bulk of the watercraft at a point above the transom where it could interfere with the operator's view. In addition, the high center of gravity causes shifts in the center of gravity of the entire watercraft as the tilt and trim adjustment of the outboard motor is accomplished. Furthermore, the high placement of the powering internal combustion engine can cause it to intrude into the area forward of the transom when the outboard motor is tilted up to an out of the water position.
In addition to the aforenoted defects of conventional type of outboard motors, there are certain other defects which have been overcome by outboard motors having a construction of the type shown in co-pending U.S. letters patent Ser. No. 604,583, filed Oct. 25, 1990 entitled "Marine Propulsion Unit" in the name of Akio Onoue and Ser. No. 604,584, filed Oct. 25, 1990, also entitled "Marine Propulsion Unit" and filed in the name of Manabu Nakayama, both of which applications are assigned to the assignee hereof. Those outboard motors obviate the deficiencies of conventional outboard motors by placing the powering engine substantially forwardly of the transom of the watercraft and extending in a horizontally disposed position so that the engine output shaft rotates about a horizontally disposed axis. However, with the construction shown in those applications, the balance of the powering internal combustion engine is somewhat offset to one side of the outboard motor since the engine output shaft is located coaxially with a horizontally extending shaft of the outboard drive portion of the outboard motor which drives the vertically extending drive shaft. Although such arrangements have certain advantages, there is some advantage to insuring that the center of gravity of the outboard motor lies on the same plane that the drive shaft axis is journaled in. In addition, in order to obtain symmetry with the outboard motor shown in the aforenoted co-pending applications, the induction system is disposed horizontally and in line with the crank case chambers of the engine. In some instances, other forms of induction systems may be required or desirable.